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Historic, archived document

Do not assume content reflects current
scientific knowledge, policies, or practices.

oe

oR

Wy, BULLETIN No. 47] ¥

Contribution from the States Relations Service —
A. C. TRUE, Director

Washington, D. C. PROFESSIONAL PAPER - January 31,1917

EGGS AND THEIR VALUE AS FOOD.

By C. F. Lanewortuy, Chief, Office of Home Economics.

CONTENTS.

Page. Page.
MNETOGUCHION Sea oseciace Secon cue swciesciecccccs 1 | Preserving eggs and its effect on the house-
Description and composition of eggs.....--.- 3 Holdisupphysssecste een cosas sew cise eeres 21
Cooking and serving eggs.....-........------- 12 | Frozen eggs, desiccated eggs, and egg substi-
Wieestiility, Of E&ESe-sccc- ee. cc cscs sess +~ 15 ELLE OSE eo es Meine one Sk tenn aoa 24
Wholesomeness Of eggs.----..-------+--+22++5 16 | Importance of eggs as food and their place in
The supply of eggs from the housekeeper’s EEN U CLL OE ee ate ee en ete 25

Stand POM tecacccene eas cictsiss slo cos eh wos 2 = 17
INTRODUCTION.

Perhaps no article of diet of animal origin is more commonly eaten
in all countries or served in a greater variety of ways than eggs.
Hens’ eggs are most common, although the eggs of domestic poultry
other than hens are sometimes used. Guinea eggs are eaten where
they are readily obtained and are much prized for their delicate
flavor. Turkey eggs are mild in flavor and are eaten to some extent,
though they are usually too valuable for hatching to be much used as
food. Ducks’ eggs are stronger or more pronounced in flavor than
hens’ eggs, the feed apparently exercising considerable influence on
the flavor, but they are much liked by many and are now used more
than formerly. Goose eggs are still stronger in flavor. Nevertheless,
they have some use for table purposes, especially in regions where
goose raising is common. In South Africa, where ostrich raising 1s
an important industry, the eggs are used as food to some extent and
are regarded as of excellent quality for cookery. Their food value
is also recognized in those regions of the United States where os-
triches are raised.

Notrr.—This bulletin is of special interest to housekeepers and to home-economics
extension workers, teachers, and students. It summarizes data regarding the nature
and uses of eggs and the effects of methods of handling, storing, and marketing upon the
value of eggs in the household,

61389°—Bull. 471—13——1

2 BULLETIN 471, U. S. DEPARTMENT OF AGRICULTURE.

The eggs of wild birds, once commonly used, are still eaten, but
in a limited way. Plovers’ eggs are prized by epicures and the eggs
of certain kinds of sea birds have been used to some extent.t

Other eggs besides those of birds are also eaten. Turtles’ eggs are
generally highly prized and very commonly eaten where they can be
obtained. The eggs of the terrapin are served with the flesh in some
of the dishes prepared from it. Fish eggs, especially those of stur-
geon, are eaten in large quantities preserved with salt, under the
name of caviar. Shad roe is another illustration of the use of fish
egos.

Notwithstanding these minor instances, the term “eggs,” when
used in connection with food topics, refers to the eggs of birds,
usually domestic poultry, and more particularly hens’ eggs, and,
unless qualified in some way, is used in the last sense in this bulletin.

Although man has been guided by instinct and experience in the
selection of eggs for food and of birds for domestication as egg pro-
ducers, he has nevertheless chosen kinds having distinct physiological
characteristics. In this respect birds may be divided into two groups:
(1) Those in which the young are hatched full-fledged and ready in
a great measure to care for themselves, and (2) those in which the
young are hatched unfiedged and remain entirely dependent upon the
parents for some time. Hens and guinea fowls are familiar examples
of the first group; robins and sparrows of the second. The eggs of
the two classes differ materially in composition, as might be expected
from the role they play in the development of the young bird, more
nutritive material being needed in the first case than in the second,
since growth is continued in the egg until the bird reaches a more
advanced stage of development. It is interesting to note that the first
includes the birds whose eggs are economically important.

The appearance of an egg—the shell with its lining of membrane
inclosing the white and the yolk—is too familiar to need any discus-
sion. Eaeh fertile egg contains a germ, or embryo, and is at the
same time a storehouse of material for the development and growth
of the young individual until it has reached such a stage that life is
possible outside the narrow limits of the shell. The embryo is in close
relationship with the yolk, which furnishes the nutritive material for
its early development, the white being used later. Naturally, yolk
and white differ in composition as much as they do in appearance,
their food value for man corresponding to the part they play in the
growth of the chick.

99

1The danger of exterminating these desirable birds by gathering their eggs for food
has been discussed in U. 8S. Dept. Agr. Yearbook, 1899, p. 270.

EGGS AND THEIR VALUE AS FOOD. 3

DESCRIPTION AND COMPOSITION OF EGGS.
SIZE.

The eggs of different kinds of domestic poultry vary in size as well
as appearance, and there is also a considerable range in the size of
eggs of different breeds; thus, hens’ eggs range from the small ones
laid by bantams to the large ones laid by such breeds as Light
Brahmas. On an average, hens’ eggs are 2.27 inches in length and
1.72 inches in diameter, or width, at the broadest point, and weigh
about 2 ounces each, or 8 eggs to the pound (1.5 pounds per dozen).
Generally speaking, the eggs of pullets are smaller than those of old
birds, those of guinea fowls about two-thirds the size of hens’ eggs,
those of ducks somewhat larger, while those of turkeys and geese
are considerably larger.

COLOR OF EGGS AND ITS RELATION TO THEIR VALUE AND USE.

Considering both wild and domestic birds of all sorts, the eggshell
ranges from white to deep colors through a variety of tints and
mottlings. The eggs of domestic fowls are not highly colored. Those
of hens vary from white to a light or deep brownish tint, the eggs
from a particular breed being very similar as regards ial color,
though varying in depth of Ale or shade. The eggs of ducks are
bluish white; those of geese, commonly white; those of guinea fowls,
white or light brown, more or less mottled with a deeper shade; and
those of turkeys, usually speckled with a yellowish brown.

Any special coloring in the eggs of wild birds is commonly ex-
plained as a protective measure which has been developed to render
the eggs inconspicuous in their normal surroundings and therefore
less easily found by their enemies. Such reasoning would indicate
that the observed differences in the color of hens’ eggs are due to
characteristics which different breeds have inherited from remote
wild ancestors. Of common breeds, for example, Cochins, Brahmas,
and Langshans, all belonging to the Asiatic class, lay brown-shelled
egos, while Leghorns and Minorcas, which belong to the Mediter-
ranean class, lay white-shelled eggs.

The color of the shells, whatever its reason, is a feature which
~ has some effect on the market value of eggs of domestic poultry,
although not upon their food value (see pp. 4 and 6), the brown-
shelled eggs bringing the higher price, for instance, in the Boston
market, and the white-shelled eggs in the New York market. In
finelend the preference is decidedly in favor of the tinted eggs.
Such local differences probably originated i in the fact that some one
‘breed of hens was once chiefly used in a given region and us type of
eggs set the standard there.

4 BULLETIN 471, U. S. DEPARTMENT OF AGRICULTURE.

Extended investigations at some of the agricultural experiment
stations, in which many analyses were made of eggs from different
kinds of hens, have shown plainly that there are no uniform varia-
tions in the physical properties and chemical composition of brown- ~
shelled as compared with white-shelled eggs. Such tests justify the
statement that the eggs of any given breed of hens, whatever the
color of the shells, are, on an average, as nutritious as those of an-
other breed, provided the eggs are of the same size and freshness
and the fowls are equally well fed.

The color of the egg contents is also a matter of interest with
respect to market value and domestic uses. Raw egg white has a
more or less greenish tinge, which is apparently influenced somewhat
by the character of the feed, though no specific coloring matter has
been isolated from it. When the albumin is coagulated by heat in
cooking, the color varies from white to pale greenish or yellowish
tones, hard to define, yet distinct. There is a belief that eggs with
shells of the same color should show the same color in the cooked
whites and that the cooked albumin of white-shelled eggs is decid-
edly whiter than that of eggs with tinted shells. Perhaps few per-
sons carry preferences so far as to refuse an egg because of the color
of the white, yet it is stated on good authority that in high-class
hotels and restaurants, where great attention is paid to details, it
has been found that the boiled eggs served must match in color. If,
when taken from the shell, one is greenish white and the other clear
white, the eggs are often rejected on the ground that one of them is
not of the required standard of excellence.

The egg yolk owes its characteristic yellow color to a pigment
whose chemical nature has been carefully studied. The depth of the
yellow color apparently depends—in large measure, at least—upon
the presence of green feed in the ration, and pale-colored yolks indi-
cate that such feed is deficient. Though frequently the yolk is pale,
the color which we commonly regard as a standard is a decided
yellow, and so the pale-yolked eggs are often said by housekeepers
to be inferior, as a given number of such yolks impart to cake or
custard less of the yellow color regarded as an indication of richness
than do eggs of a darker yolk, a belief which chemical analysis does
not justify.

Although, as stated above, variations in color do not imply vari-
ations in food value, it is not at all unlikely that there are differences
in flavor corresponding to the color of the egg yolk, that which is
deep yellow having a more pronounced flavor than the pale one. At
any rate, as long as preference for deep-colored yolks and pale
whites exists, the poultry raiser who caters to a fancy market should
take such factors into account.

EGGS AND THEIR VALUE AS FOOD. 5

FLAVOR OF EGGS AND FACTORS AFFECTING IT.

It is generally conceded that eggs which are perfectly fresh have
the finest flavor. After they have been kept for a time, the flavor
deteriorates, even if there is no indication of spoiling. Such dif-
ferences are especially important when eggs are used for table pur-
poses. Stale eggs are not regarded as palatable, and the flavor of
spoiled eggs is such that for this, if for no other reason, they are
totally unfit for food. The flavor of even perfectly fresh eggs is not
always satisfactory, since it is influenced more or less by the charac-
ter of the food eaten by the laying hens, eggs produced on highly
nitrogenous rations, for instance, being inferior to those from a car-
bonaceous ration. Highly flavored food, such as wild-onion tops
and cabbage, may also have a bad effect on the flavor of the eggs pro-
duced. This is a matter of importance, especially when poultry is
kept to supply eggs for table use.

COMPOSITION.

The shell of a hen’s egg constitutes about 11 per cent, the yolk
32 per cent, and the white 57 per cent of the total weight of the
egg. The shell of a duck’s egg constitutes about 14 per cent of
the total weight and that of a plover’s egg 10 per cent. The propor-
tion of white and yolk varies somewhat with different breeds of hens,
the proportion of yolk being greatest in bantam eggs and, in general,
greater with those breeds which are best suited for fattening than
with others. Brown-shelled eggs have been found to have a somewhat
heavier shell than white-shelled eggs.

The following table shows the composition of hens’ eggs (raw and
cooked, brown shelled and white shelled) and of egg white and yolk,
as well as the composition of the eggs (whole egg, white, and yolk)
of guinea fowls, ducks, geese, turkeys, plovers, etc., and that of evap-
orated eggs and egg substitutes. For purposes of comparison the
composition of several other familiar foods is also included.

6 BULLETIN 471, U. S. DEPARTMENT OF AGRICULTURE.

Average composition of eggs, egg products, and certain other foods.

{

A Fuel
Refuse. | Water. | Protein. Fat. | verbal “| Ash. ae per
ates.
| pound.
Hen: Per cent.| Per cent. | Per cent.| Per cent. | Per cent. | Per cent.| Calories.
Whole egg as purchased... -. | 11. 2| 65.5 | 11.9 OS see ee ae 0.9 595
Wholeegg, edible portion..--- {UR eee t 73.7 13.4 1 Re es Regen, | 1.0 670
BWililGGsse menace oo ois ne nae Soe ena kes 86.2 12.3 Sa ALAS Ee 6 230
Wolic ie oie: ER Sea ns | eee 49.5 rey Alias) Ge me 1.1 1,645
Whole egg boiled, edible por- |
Be ole eee ere eh aad Eh eee ne /Blg 13.2 12:0 ee .8 730
Duck:
Whole egg as purchased..--. IBY 4) 60.8 | iba TOE lo Speers 8 730
Whole egg, edible portion.-..).........! 70.5 13.3 5 Me) eee ee 1.0 835
Rihites 2222.82: coats ae Esra 11.1 A030 Nee ae .8 200
Ge ee nepal Bl he | 45.8 16.8 SOLD) Bee ee 1.2 | 1,785
Goose:
Whole egg as purchased... .. 14.2 59.7 12.9 | AES sore eee 9 | 755
Whole egg, edible portion....|......_.. 69.5 13.8 1A Aloe Sea 1.0 840
WVATLOLo tenes een ee) ee eee 86.3 11.6 Bt Te -al Napa ees Su 210
BV O1KS ho 5 Se aS Been ai ae 44.1 Lifes 3622) 455 eee ees 1.3 1, 790
Turkey:
Whole egg as purchased..... 13.8 63.5 12.2 Oe ihe | atag bale 8 615
‘Whole egg, edible portion....|.......--| (BRT! 13.4 LE 2 eee ee .9 700
WiDILO tee Saaet eee ae eee eae 86.7 ARS £03) eas eee 8 210
PNiolics eee oon ane a (Ee aes 48.3 1724; © 32508 |e eee 1.2 1, 660
Guinea fowl]:
Whole egg as purchased -..... 16.9 60.5 11.9 929). oak tees 8 620
Whole egg, edible portion... .|........- 72.8 ibys TD* Obs eee es eee 9 735
WWE CEL Sa See Bs Sa ae aa es ee ee 86.56 11.6 3033 |e se eee -8 210
Ol festa be Nee ent oe SRE ces 49.7 16.7 F158 eae 1.2 1, 600
Plover ; |
Whole egg as purchased 2.... 9.6 67.3 9.7 LOSGi es ke ees 9 610
Whole egg, edible portion 2..|......._. 74.4 10.7 a fehl bee ae 1.0 670
Fresh-water turtle eggs 2..-......|......... 65.0 18.1 tLe ie eee 2.9 780
Nea-LUTieGses 2 -c 5 Fe er Aaa eee vee 75.4 18.8 OF Sh eee eee -4 740
palted@duckiegesizcces Sse als Paes 68.0 12.0 O:2 alba SEES 4.0 595
Desiccated hens’ eggs:
Whole egg........... Je gis: ee 6.4 46.9 36.0 rte] 3.6 2,450
WiNibO state cee Se ee oe eee te iB (83x -o 8.6 | 6.2 1,495
GE aay Pa Ran er a |S kep ee 5.9 srs e4 PSie6 ot | 3.5 2, 815
SSIS DSLIL Lenssen eee a eee | 11.4 73.9 3 5.3 9.1 1, 450
Pudding (custard) powders ?....|......... 3.0 Pasi 3.4 80.9 } .6 1, 645
Sad Opie ee eee roe cen nl ce tee | 71.2 20.9 3.8 2.6 1.5 580°
Caine eee ee ye Ore ee Bests ae 48.0 29.3 14.0 1.3 7.4 31,125
Cheese (full cream) as purchased.|..._..._- 34.2 25.9 33.7 2.4 3.8 1, 890
Sirloin steak as purchased - .---.- 12.8 54.0 16.5 Lied be eee ao 955
Sirloin steak, edible portion...... eters 61.9 18.9 19:5 see ee 1.0 1, 100
Malicers eS 8 et pa ate Solas A ae 1. SORT G 351 leap 5.0 7 315
Oysters, edible portion........... | Sa ca 86.9 6.2 | EP 3.7 2.0 230
Wiheab fore s2 Sean: Bir as 6. | set ee 12.0 11.4 | i.0 riya! 5 1,610
Potatoes as purchased............, 20.0| 62.6 1.8 ef 14.7 .8 305
Potatoes, edible portion.........- lissd ss gga ‘nf BES 2.2 il 18.4 | 1.0 380

1 These values were calculated on the assumption that protein and carbohydrates (each) yield 1,820 (or 4
calories per gram) calories per pound; and fat, 4,080 (or 9 calories per gram) calories per pound.

2 European analyses.

3 Including 6.2 per cent common salt.

The above figures represent average values. Individual speci-
mens vary more or less from the average. :

As shown by analysis, eggs consist chiefly of two nutrients, pro-
tein and fat, in addition to water and mineral matter, or ash. Car-
bohydrates, valuable in the diet as a source of energy, are present in
such small amounts that they are usually:not determined in anal-
ysis—ducks’ eggs containing only 0.3 per cent, hens’ eggs 0.67 per
cent, turkeys’ and guinea fowls’ eggs 0.8 per cent each, and goose
eggs 1.3 per cent. An exception is found in the case of plovers’
eggs, which have been reported to contain over 2 per cent. As re-
gards distribution, about one-third of the carbohydrates occur in the

EGGS AND THEIR VALUE AS FOOD. 1

yolk and two-thirds in the white. The most abundant nutrient is
protein or nitrogenous matter, of which three-fifths of the total
is present in the white and two-fifths in the yolk. Protein supplies
nitrogen needed to build and repair the body tissue, and also some
energy, being equal to carbohydrate in this respect, although inferior
to fat, as noted on page 9.

It is sometimes convenient to consider the relations of protein and
energy in a definite amount of foodstuffs. In the case of a whole
egg, 2.4 ounces of the edible portion would be required to supply 100
calories of energy, of which the protein would contribute 36 calories.
Of white, 6.9 ounces would be needed to supply 100 calories, and of
this amount 97 calories would be contributed by protein. In case
of the yolk, 1 ounce will supply 100 calories, of which protein con-
tributes 17.

Mineral matter is required by the body for building bone and other
tissue and for regulating the ‘body processes. In addition, recent
research has shown that certain accessory substances (so-called vi-
tamins, for example) are also present, which are required by the
body in at least minute amounts. Since eggs contribute to all these
body needs, their value as food is evident.

In composition eggs resemble such animal foods as meat, milk,
and cheese, more than such vegetable foods as flour and potatoes.
As will be seen by the figures in the above table, hens’ eggs and those
of other poultry do not differ greatly in composition. Furthermore,
there is practically no significant difference in composition between
hens’ eggs with dark shells and those with white shells, although
there is a popular belief in some localities that the former are richer.
Neither does the cooked egg vary materially in composition from the
raw, though it varies markedly in texture. The yolk and the white,
on the other hand, differ greatly in composition, the yolk containing
considerable fat and ash, and the white being practically free from
fat and containing somewhat less protein and ash and considerably
more water than the yolk. Though both yolk and white, when raw,
are fluid, they are not thought of as containing water any more than
other familiar foods in which water is not visible as such but com-
bined or mingled with the other constituents so that the whole food
is more or less moist, liquid, or juicy. This and similar facts are
brought out in figure 1, which shows in diagrammatic form the com-
position of eggs and egg products.

Though eggs are conceded to be a nutritious food, they are less
concentrated, that is, they contain more water than some—cheese,
for instance. On the other hand, they are more concentrated than
many others, milk or oysters, for instance, and on the whole do not
differ greatly in this respect from lean meat. Their general resem-
blance in composition to other common animal foods suggests that

8

BULLETIN 471, U. S. DEPARTMENT OF AGRICULTURE.

they may be properly used in the diet in the same way, an idea
confirmed by almost universal experience. Such facts are brought
out in figure 2, which compares eggs and a number of other common

foods.

Va
FOS %s WATE
0S. ZPROTEIV

BI. 3BXLFA Gre

C6. 2L UATE? \ ;
eA apon BBG |

LG OP 4 LAT = us
06% AS: 2
L6G MINIT E
73.756 WATE/?P

i... 6 FAT
1O% ASt1
DESICCATED L£6C
ace _ SUBSTITUTE

j CAP BOHN Y OPATE li f
sa eat 2.1%. 45th

Fic. 1.—Chemical composition of egg yolk, egg white, desiccated egg, and egg substitute.

As sources of energy in the diet, eggs supply per pound a larger

number of calories (the common heat unit) than does milk, and
fewer than does beefsteak or white bread. This and other facts re-
garding the energy value of eggs and egg products as compared
with some other foods are shown graphically in figure 3. A pound
of egg yolk has a much higher energy value than a pound of egg

‘ee

EGGS AND THEIR VALUE AS FOOD. 9

white, as will be understood when it is recalled that it is the yolk
which contains the egg fat and that this constituent has an energy
value per pound two and one-fourth times as great as either protein
or carbohydrates. Egg yolk approaches full-cream cheese in energy
value and has about two-thirds the energy value per pound of bacon,
one of the common foods which are characterized by a very high fat
content. Desiccated egg, as is the general rule with foods which

ex WATEIP 87.0%
: [JVI FPPOTEIN = F-F76
Z

QTL EO DI OAT SAT BOP WY sy
/O%A 5 CARBO YOFATE 5.07. SEE o ney

WITLE LOC WILLE

CV OK

“TOUASH
BEEF STEAL

SE Oo —>
FPOTE/N

$4 2K, WATE? GES

SAF FAT 43%
ae | 22% CARBON VORATE FEL Z0\

Ze

LP, ASH ASH UL Le

Fig, 2.—Chemical composition of eggs as compared with that of some other common foods.

have been concentrated by the evaporation of water, has a much
higher energy value per pound than the fresh eggs.

As regards the specific nature of the different nutrients in eggs,
much information is available. Egg white, formerly said to be pure
albumin, is now known to contain, in addition to small amounts of
carbohydrates, two distinct forms of albumin and a very little
mineral matter, chiefly sodium chlorid (common salt). Phosphorus
is also present, the amount being equivalent to about 0.03 per cent
phosphoric acid.

61889°—Bull. 471—17——2

10 BULLETIN 471, U. S. DEPARTMENT OF AGRICULTURE.

A very extended investigation of the white of egg was made at the
Connecticut State Experiment Station. The “albumen” or protein

STANDARD FOP COMPA/SONWV

4000 CALORIES
PEP POUND

WHOLE ECG PHILA
670 OFZ. — AS CAL.

EGC FOLIC © FULL:CRENA CHEESE
LOGS CAL. 4890 CAL.

£66 WHA 7F BLE I STLAL
230 CAL. 4090 CAL.

DESICCATED ECC WHITE BREAD
2,950 CAL, 4,185 CAL.

LCC SUBSTITUTE BACON
4,F50 CAL. 2,930 CAL.

Fic. 3.—Energy value of eggs as compared with that of some other common foods.

EGGS AND THEIR VALUE AS FOOD. 11

of egg white was found to consist of four bodies—ovalbumen, con-
albumen, ovomucin, and ovomucoid. The ovalbumen is the chief
constituent and makes up the greater part of the egg white. The
conalbumen has much the same chemical properties as ovalbumen.
Ovomucin and ovomucoid are glycoproteids, and are present in small
amounts.

Egg yolk contains a number of different bodies, including about
15 per cent vitellin (a protein) ; 20 per cent palmitin, stearin, and
olein (in the fat); and 0.5 per cent coloring matter (see p. 4), be-
sides some nuclein, etc., lecithin (a fat-like body containing phos-
phorus and now regarded as one of the very important food consti-
tuents, as it furnishes the body with phosphorus in a form in which
it may be readily assimilated), and vitamins (see p. 7). Besides
phosphorus, equivalent to a little over 1 per cent of phosphoric acid,
the yolk contains such mineral elements as iron, calcium, and
magnesium.

Since in all cases the egg is designed to furnish the sole source ot
material for growth and development of the young individual for a
considerable time, it 1s evident that it must contain all the elements
required ; that is, it must be a complete food for the purpose intended,
and this goes far to explain why it 1s such a valuable food for man.
Milk is another familiar example of animal food containing all the
elements of a complete food for the young and growing individual,
and milk and eggs are frequently, though inaccurately, spoken of as
perfect foods on this account and have always been considered espe-
cially important in the diet of invalids and children. It is true that
they contain all the required elements for the growth and mainte-
nance of the young mammal or the young bird, as the case may be,
but this is not the sole test, for the elements are not in the right pro-
portion for the sole nourishment of an adult individual. Man seems
instinctively to have recognized this, since he uses eggs, as he does
milk, in combination with other foods.

Though rich in iron and calcium, eggs contain an excess of nitro-
gen, phosphorus, and sulphur, and are, therefore, a predominantly
acid food; that is, in the process of digestion an excess of acid end
products is formed which the well-being of the body requires should
be neutralized with basic substances, best supplied by such foods as
fruits, vegetables, etc. The nitrogenous material in eggs, as in milk,
is readily assimilated. It is especially noticeable that neither milk
nor eggs contain purins, substances which are convertible into uric
acid. In general, the iron, phosphorus, calcium, easily digested pro-
tein, and fat in eggs make them rank high in the list of foods in a
_ well-selected dietary.

Many experiments have recently been reported concerning the pres-
ence in eggs of such substances as the so-called vitamins and the lipoid-

12 BULLETIN 471, U. S. DEPARTMENT OF AGRICULTURE.

like bodies which are thought to maintain the equilibrium of nor-
mal nutrition and to stimulate growth. As yet there is not unanimity
of opinion as to the nature or the amount of these substances needed.
It seems certain, however, that they are rather widely distributed and
that a diet containing eggs, milk, fruits, and the other common foods
in wholesome variety is likely to supply a sufficiency.

One of the constituents of egg albumin is sulphur, and the egg
albumin is readily decomposed with the liberation of hydrogen sul-
phid. The bad odor of rotten eggs is due largely to the presence of
this gas and phosphureted hydrogen, which is also formed. The shell
of the egg is porous, and microorganisms which cause the egg to rot,
or spoil, may gain access through the minute openings, and some of
these in their growth cause the formation of these sulphur com-
pounds. Even when a fresh egg is cooked, some sulphur is liberated,
as is proved by the blackening of silver spoons or forks when they
come in contact with boiled eggs. It is a matter of common observa-
- tion that when eggs are boiled the yolk where it joins the white
cften has a more or less greenish color. Rubner has found that this
discoloration is due to the action of the hydrogen sulphid produced
by boiling on the iron of the vitellin of the egg yolk in the presence
of alkali (formed when the white comes in contact with the yolk).

In the table no figures are given for the composition of the egg-
shell, which, of course, is not used as food, though in times past it
has had some use in domestic medicine. The shells of hens’ eggs are
made up very largely of mineral matter, containing 93.7 per cent cal-
cium carbonate, 1.3 per cent magnesium carbonate, 0.8 per cent cal-
cium phosphate, and 4.2 per cent organic matter. The shells of goose
eggs, on an average, have the following percentage composition:
Calcium carbonate, 95.3; magnesium carbonate, 0.7; calcium phos-
phate, 0.5; and organic matter, 3.5. The shells of ducks’ eggs contain
94.4 per cent calcium carbonate, 0.5 per cent magnesium carbonate,
0.8 per cent calcium phosphate, and 4.3 per cent organic matter. The
shells of other eggs are doubtless of much the same composition. ~

COOKING AND SERVING EGGS.

Methods of serving eggs, alone or in combination with other food
materials, are very numerous. Those in which eggs are cooked
alone—for instance, boiling, frying, shirring, and poaching—are, in
general, simpler than those in which they are combined with other
materials.

As regards the uses of eggs in cookery, they serve to improve the
flavor, color, and texture of such foods as cakes, while in such dishes
as custards and creams they also serve to thicken the material and to
give it the desired consistency.

:

EGGS AND THEIR VALUE AS FOOD. 13

When beaten or whipped, eggs, and particularly egg whites, in-
close air bubbles, many more being inclosed by fresh eggs than by
packed or old eggs. When such beaten yolks and whites are added
to batters or doughs the air bubbles are distributed throughout the
mass, and when the dough is cooked the inclosed air expands and the
walls of the air bubbles become firm, with the result that the porous
structure is retained. Sponge cake and angel cake are familiar
examples of foods made light with eggs. It is interesting to note
that recipes for cakes and similar dishes to-day commonly call for
fewer eggs than those of a generation or two ago. The reason is
that, owing to the quite general use of baking powder, the house-
keeper is not so often compelled to depend upon eggs to make her
cakes light and need use only enough to give the desired flavor, color,
and texture. In considering the uses of eggs as an ingredient of
cakes and other dishes, it should be noted that they add materially
to the nutritive value of the dish as well as to its quality and
appearance.

Besides their uses in foods of various sorts, eggs are often em-
ployed as a garnish. Hard-boiled eggs, for instance, cut into dif-
ferent shapes, are a common garnish for cooked greens or for salad;
or, instead of being cut or chopped, the yolk may be put separately
through a ricer.

White of egg is employed for icings, meringues, and confectionery,
particularly various sorts of cream candy, and for clarifying liquids
(see p. 14).

Since eggs are especially rich in protein, combining them with
flour, starch, and sugar (typical carbohydrate-yielding foods) and
butter and cream, which are rich in fat, is perhaps an unconscious
effort to prepare a food which shall more nearly meet the require-
ments of the body than any one of the ingredients alone. When
eggs, meat, fish, cheese, or similar foods rich in protein are eaten,
such other foods as bread, butter, potatoes, etc., are usually served at
the same time, the object being, even if the fact is not realized, to
combine the different classes of nutrients into a suitable diet. The
wisdom of such combination, as well as of other generally accepted
food habits, was proved long ago by practical experience. The reason
has been more slowly learned.

The total number of methods of serving and preparing eggs is
very large, but in nearly every case each is only a more or less elab-
orate modification of one of a few simple ways of cooking. Thus, an
egg in the shell is cooked by immersion in hot or boiling water or is
less commonly roasted. An egg removed from the shell may be
cooked in hot water or in hot fat. In the latter case it may or may
not be beaten or stirred. Combined with other materials to form

14 BULLETIN 471, U. S. DEPARTMENT OF AGRICULTURE.

various made dishes, eggs are boiled, baked, steamed, or fried, as the
case may be.

Changes in weight are often noted when foods are prepared for the
table. These vary with the kind of material and the method of prepa-
ration, but, in general, loss in weight is due to volatilization, and gain
to the absorption of water. Much careful experimenting with eggs
cooked in the shell shows that if the egg remains in water a few min-
utes it loses only a very little material, probably water, which passes
out through the porous shell. If it is left in the water for a longer
time it may gain weight by absorbing water. In either case the
change is too small to modify the food value of the egg appreciably.

Different methods of cooking cause marked changes in the appear-
ance and structure of eggs. Thus, boiled eggs—that is, eggs cooked
in the shell in hot, though not necessarily boiling, water—vary greatly
in hardness, according to the length of time the cooking is continued,
the method of procedure, etc. The directions commonly given for
preparing soft-cooked, medium-cooked, and hard-cooked eggs vary.
Any of them without doubt will give the desired result if sufficient
care is exercised. The chief difficulty is in securing uniform results,
especially with soft-cooked or medium-cooked eggs. It must be re-
membered that such results can not be expected when conditions vary.
The time of cooking, the quantity of water used, the number, size,
freshness, and temperature of the eggs, and the kind of vessel used
are important factors. Thus, eggs which have been kept in an ice
chest require more heat to warm them before cooking begins than do
those which have been kept at room temperature. Again, so appar-
ently trivial a detail as the sort of vessel used (whether earthen or
metal), or the place where the vessel stands during cooking, may pro-
duce different results. Even after the eggs are taken out of the water
they may continue to cook, and the length of time they stand before
using may make a noticeable difference in their consistency. Many
persons prefer to have eggs cooked at the table in a chafing dish or
other suitable vessel. In such cases the conditions may be controlled
with comparative ease, and uniform results obtained with a little
practice and care.

As previously stated, egg white, when heated at the temperature of
boiling water for a considerable time, becomes hard and contracts.
This explains the curdling of custards and the shrinkage and tough-
ening of omelets, soufflés, meringues, sponge cake, and similar mix-
tures. The firm coagulation of albumin at 212° F. explains the use of
egg white for clarifying coffee, soup, or other liquids. The albumin,
which is mixed with the liquid before boiling, coagulates and incloses
the floating particles, leaving the liquid clear. When eggs are re-
moved from the shell, a little of the white usually clings to the inner
surface unless it isscraped. Such eggshells are often used for clarify-

EGGS AND THEIR VALUE AS FOOD. 15

ing purposes instead of the whole egg (see p. 18). The clarifying
properties are, of course, due tc the egg white and not to the shell.
Eggs are also employed in the arts, for instance, the use of egg
white in the manufacture of albumin paper and of egg-yolk oil in fin-
ishing leather.
DIGESTIBILITY OF EGGS.

Eggs are commonly said to be very digestible, especially when
raw or slightly cooked. Probably most persons would understand by
this that they digest without giving rise to pain or other physical dis-
comfort. This is undoubtedly true, but the word “ digestible” has
another meaning in most discussions of food values. It refers not
only to the ease, but also to the thoroughness, of digestion—that is,
to the total amount of material that the food gives up to the body in
its passage through the digestive tract. The original nature and
condition of a food, the method of cooking, and the quantity eaten
at a given time are among the factors that determine the amount of
any given material that can be digested, but, in general, it is fair to
say that the variations are less than is commonly supposed, the quan-
tity of undigested food excreted from the body being usually very
small.

Statements often far from accurate are frequently made with
regard to the length of time required to digest different foods. Some
of them are based on investigations (some old and some recent) which
take into account chiefly the Jength of time food remains in the
stomach, assuming that this represents digestion and forgetting that
digestion in the intestines must also be considered. Other statements
are based on artificial digestion experiments in which the food is sub-
jected in the laboratory to the action of digestive ferments which
occur in the body. It is probable, however, that all the conditions
of digestibility in the body can not be reproduced in the laboratory,
and, although the results obtained are interesting and often valuable,
it is worthy of note that careful investigators are much slower to
make sweeping deductions from them than are popular writers on
the subject.

As regards thoroughness of digestion, that is, the proportion of
nutritive material the body retains from a given food, eggs rank high,
reliable experiments having shown that, on an average, 97 per cent of
the protein and 95 per cent of the fat are assimilated.

The question as to whether eggs are more or less digestible raw,
slightly cooked, or hard cooked has also been studied by a number of
investigators, the results indicating that, while cooking makes some
difference with the rate (as shown by test-tube work), it makes little
with the thoroughness of digestion. Even as regards quickness of
digestion there is little difference between raw and slightly cooked

16 BULLETIN 471, U. S. DEPARTMENT OF AGRICULTURE.

eggs. Inthecase of hard-boiled eggs the yolks are probably as digesti-
ble as those of less thoroughly cooked eggs. However, the whites are
so firm in texture that, unless they are finely chopped or thoroughly
masticated, the digestive juices will not be able to permeate them
quickly, and so portions may escape digestion or remain in the di-
gestive tract for several days and decompose. This explains why
hard-boiled eggs are often excluded from the diet of little children
and invalids and suggests that even healthy adults should be careful
to masticate them thoroughly. j

From all the evidence it seems fair to conclude that eggs are very
thoroughly digested and that the length of time of cooking has less
effect upon this factor than upon the time required for digestion in
the stomach. In a healthy man the latter consideration is probably
not a matter of much importance, as digestion will continue in the
intestine. In the diet of invalids it may be more important. How-
ever, diet in such cases is a matter for the attention of skilled physi-
cians, and one should be guided by their advice.

Apparently there is no reason for believing that ordinary breakfast
beverages (tea, coffee, or cocoa) have any marked effect upon the
thoroughness of digestion of eggs, notwithstanding the popular
statement sometimes made to this effect.

WHOLESOMENESS OF EGGS.

Eggs are wholesome as well as useful and nutritious food. Over-
indulgence may lead to digestive disturbance, as it may with any
food, but, on the whole, eggs can be eaten by most people in usual
quantities without such results. Occasionally, however, a person is
found who is habitually made ill by eating eggs, just as there are
those who can not eat strawberries or other foods without distress.
Such cases are due to some personal idiosyncrasy, showing that in
reality “one man’s meat is another man’s poison.” ‘The physiologi-
cal explanation for them is probably that these persons have become
abnormally sensitized to a specific protein body in the egg which will
then act as a poison when digested and taken into the circulation.

Under certain conditions eggs, like other foods, may be accidental
carriers of disease by conveying to the body harmful bacteria or
parasites. It is possible for an egg to become infected with micro-
organisms, either before it is laid or more especially after it is
jJaid, since the porous shell offers no great resistance to microorgan-
isms, including those which cause it to spoil or rot. If an egg is eaten
raw or only slightly cooked, microorganisms, if present, can be com-
municated to man and may cause disease if they are of the sort to do
so. If an egg remains in a dirty nest, for example, defiled with the
microorganisms which cause typhoid fever, carried there on the hen’s
feet or feathers, it is not strange if some of these bacteria occasionally

EGGS AND THEIR VALUE AS FOOD. iby

penetrate the shell and the egg thus becomes a possible source of
infection. Perhaps one of the most common troubles due to bac-
terial infection of eggs is the more or less serious illness sometimes
caused by eating those that are stale. This, often called ptomaine
poisoning, is more correctly styled food poisoning, and is caused
by microorganisms that are commonly associated with filth.

Judged by the comparatively small number of cases of infection
or poisoning due to eggs, reported in medical literature, the danger of
disease from this source is not very great. However, in view of its pos-
sibility, it is best to keep eggs as clean as possible and thus endeavor to
prevent infection. Clean poultry houses, poultry runs, and nests are
important, and eggs should always be stored and marketed under |
sanitary conditions. The subject of handling food in a cleanly man-
ner is too seldom thought of, and what is said of eggs in this connec-
tion applies to many other foods with even more force. Since it is
not wise to wash eggs that are to be kept, only clean ones should be
selected for this purpose. Always, when eggs are used, the shells
should be carefully cleaned just before they are broken, as otherwise
any dirt present on the outside may find its way into the food.

Occasionally the eggs of worms, etc., have been found inside hens’
egos, as indeed have grains, seeds, etc. Such bodies were doubtless
accidentally occluded while the white and shell were being added to
the yolk in the egg gland of the fowl. This isa rare occurrence and
has little to do with the general question of the wholesomeness of the
ege. If it should occur the egg should not be used. The bloody spot
often found in eggs shows that growth of the embryo has proceeded
too far for the egg to be considered of desirable quality.

In general, if one actually has an idiosyncrasy toward eggs one
should avoid them. Others should do all they can to secure clean,
good eggs, and may then rest assured that these are likely to Bon
wholesome.

THE SUPPLY OF EGGS FROM THE HOUSEKEEPER’S STANDPOINT.

In order to purchase eggs to the best advantage the housekeeper
should be familiar with the source of supply. A generation or so
ago each locality depended upon its own farms for eggs, but with
the growth of cities and the resulting increased demand this state of
things has changed. The eggs raised in the Atlantic and Pacific
States are still mainly consumed in or near the place of production,
but they are not sufficient to supply these regions, and it is necessary
to ship into these regions large quantities of eggs from several of
the States of the Mississippi Basin, which produce many more eggs
than can be used there. Refrigerator cars, cold-storage warehouses,
and special cases devised to prevent breakage make it possible to ship

18 BULLETIN 471, U. S. DEPARTMENT OF AGRICULTURE.

eggs long distances and keep them for fairly long periods in good
condition.

When the housewife depends upon eggs from her own hens, or
even when she or the grocer buys direct from a local producer, she
can expect to get eggs less than a week old, and the term “ fresh-laid
eggs” has some meaning. When, however, she buys them in city
markets, especially during the autumn and winter months when hens
are not laying freely, the chances are that all except a very few high-
priced eggs purchased from some local producer were laid at least
several weeks before and very likely hundreds of miles away. This
does not means that city-market eggs are necessarily bad eggs. On
the contrary, when handled by good methods, they may be better in
quality than fresh local eggs that have been improperly cared for.

The housekeeper’s problem in selecting eggs is complicated by the
fact that it is hard to tell the quality of an egg from its appearance.
There is undoubtedly a quality in the absolutely fresh, clean egg
which is not found in any other and which will last only a day or two
under the best of conditions and can not always be secured even in
new-laid eggs. This change or loss of quality depends quite as much
on the character and cleanliness of the egg and the conditions under
which it is held as on the length of time it is kept. Since examination
is now almost a necessity in the trade, and the importance of reliable
standards of excellence is being recognized the housekeeper should
be familiar with the commercial methods.

The main points by which an expert judges the quality of an egg
are size, shape, soundness and cleanliness of the shell, and appearance
of the interior when candled (held against an opening which permits
light to shine through the egg). When an egg is newly laid, its con-
tents seem to fill the shell, as it is seen against the candle, but very
soon an air space begins to appear in one end and gradually increases
in size until it may fill even half the shell. This shrinking is due to
the evaporation of water through the porous shell, and as it increases
the weight of the egg decreases. Hence, the old household floating
test for eggs—fresh ones sink when put into a pail of water, while
old ones float. When a fresh egg is candled the yolk is barely dis-
tinguishable from the white, save as a slightly darker area in the
center of the egg. In older eggs the yolk looks darker and often shifts

its place in the egg. Various kinds of dark spots and blotches may

also develop, due to different causes, but all indicating a spoiling egg.
When all of the egg meat looks dark in candling the egg is rotten.
The art of candling is easily learned and often practiced by house-
keepers.

The housekeeper can buy more intelligently if she knows how eggs
are graded in the trade and that prices vary accordingly. The grades
are commonly designated: “ First quality ”—large, fresh eggs with

EGGS AND THEIR VALUE AS FOOD. 19

clean, uncracked shells, free from spots or blotches in candling and
weighing at least a pound and a half per dozen; “second quality ”—
eggs which would rank as first except that they either are undersized
or have begun to shrink, or eggs in which chick development is just
beginning, but has not reached the stage when a blood ring appears.
“ Dirties” are what the name implies and are always sold at low
prices, even when large and fresh. “Checks” are eggs with cracked
shells; when the cracks are large enough to let the contents escape,
_ they are called “leakers”; when the cracks are too slight for this
they are called “blind.” Both of these grades may be sold as food,
but they do not keep properly, and they bring low prices. “Spots”
and “rots” of various kinds are rarely sold in the shell at retail for
table or cooking use, though it is said that large quantities find their
way into cheap bakeshop and cheap restaurant dishes, and have at
times been used by unscrupulous manufacturers in the preparation
of frozen and desiccated products. Many such eggs are used also
in tanning leather and for other technical purposes.

The spoiling of eggs is due to two sets of causes, first, the germina-
tion of fertile eggs and development of the chick, which is a natural
process; and, second, the decomposition by molds or bacteria due to
accidental causes. Considering the eggs she keeps on hand at home,
as well as those she buys, the housekeeper should realize that each is
likely to occur if proper handling and care are lacking and that both
are preventable. The surest method of preventing losses due to the
development of the embryo is the production of infertile eggs.
Mating is, of course, essential to the development of the chick, but if
the cocks are separated from the hens as soon as the hatching season
ends in the early summer, a large percentage of the loss from bad
eggs may be avoided. This is as well worth attention when eggs are
home produced as it is in professional poultry raising.

Too much warmth favors both incubation and decomposition, espe-
cially in the case of newly-laid eggs. Eggs should be collected
promptly and kept in a cool place, especially during hot weather, for
heat is just as harmful during the first few days after eggs are laid
as it is later, and no amount of care in pantry and refrigerator or in
packing rooms, refrigerator cars, and warehouses can give back the
good quality to eggs that have lain for several days in a hot nest,
been kept in a warm pantry, or been exposed to the hot sun on their
way to town.

The loss of quality, due to molds and bacteria in the egg is brought
about by their growth and by the chemical compounds, formed by
them, which give spoiled eggs their peculiar appearance, taste,
and odor. Some of the microorganisms produce a musty taste, and
others produce compounds of sulphur and the characteristic odor of
rotten eggs. As has already been pointed out (p. 16), some of these

20 BULLETIN 471, U. S. DEPARTMENT OF AGRICULTURE.

molds and bacteria are not injurious to health, while others may
give rise to more or less serious illness. The best way to prevent
the infection of eggs by molds and bacteria is to produce infertile
eggs and to keep them clean and dry from the time they are laid
until they are finally used. The coating of mucilaginous material
on the outside of the egg and the very thin membrane, or “ skin,” on
the inside protect the egg from the invasion of molds and bacteria.
The shell coating is easily removed by water or by rubbing. Also as
eggs grow old the natural protection of the egg becomes less effective.
Therefore, deterioration due to molds and bacteria is more likely to
occur if the egg is washed or the shell becomes moist by being kept in
a damp place. If eggs are dirty enough to wash it is better to do so
and use them at once than to “put them down.” Neglected and
stolen nests (usually dirty and so sources of bacteria, etc.) are prob-
ably the chief cause of molded or rotten eggs, and so hens should
always have clean, airy nests. Housekeepers who are careful will
not choose dirty eggs. If for any reason they must be used es
should be carefully washed and wiped.

These causes of spoiling are important matters for the house-
keeper, since they have a bearing on supply and market price. It is
to the housekeeper’s interest to have only eggs produced under good
conditions brought to market, because this means less loss in handling
and an increased supply of S088 eges, which in turn, affects prices
favorably.

As a means of securing a supply of fresh eggs for baliley purposes,
the purchase of eggs direct from the producer by parcel post is worth
consideration by the housekeeper.

Since eggs vary more or less in size and weight, though very little
in composition (see p. 6), it follows that they vary in the amount
of food material which they supply. For this reason housekeepers
who have a choice very commonly like to select large eggs. That
size has an effect on the cost of eggs when they are purchased for a
uniform price per dozen is evident when one considers that a dozen
pullets’ eggs, weighing 18 ounces, at 25 cents per dozen, supplies
egos at 22.9 cents per pound, while hens’ eggs, weighing 24 ounces
at the same price per pound would supply eggs at 16% cents per
pound. Such differences are especially worth considering when eggs
are used in quantity. There are few exact household standards for
cookery, and using eggs as they come, by number rather than by
weight, would probably not imply important variations. However,
it is well known that when a recipe calls for 4 eggs one may use
instead of 4 of average size either 3 large or 5 small ones.

For reasons of economy as well as accuracy in cookery there is a
growing tendency to use eggs by weight or measure instead of by

Se

EGGS AND THEIR VALUE AS FOOD. 91

number. Obviously, such a plan is actually, though not relatively,
more economical when large recipes are used, as in boarding houses,
hotels, or public institutions, than it is in a home where the family
is small.

PRESERVING EGGS AND ITS EFFECT ON THE HOUSEHOLD SUPPLY.

Preserving eggs in one way or another seems to be almost universal
and to have been practiced for a very long time, and presumably, like |
many other everyday things, owes its origin to the observation and
experience of generations. The object usually sought is to keep
eggs as nearly as possible as they are when new laid. It is not with-
out interest to note that in some regions, notably the Orient, ripening
is sought as well as preservation. To insure this the eggs are buried
or coated with earth, brick dust, clay, or some other substance, and
kept for weeks or months, when they undergo a fermentation or
ripening and acquire such a texture and flavor that they are often
compared with “ripe” cheese. Egg preservation such as we are
familiar with is the opposite of this and attempts not only to prevent
such ripening processes, as well as putrefactive changes, but also to
hinder or prevent any bacterial or other changes which lessen original
quality.

The whole matter of preserving eggs is of importance to the
teacher of home economics and the housekeeper, for not only does the
housewife preserve eggs for her own use, but the available supply of
those she purchases and their cost are directly influenced by such
factors.

As regards home storage, housekeepers under most circumstances
must keep eggs on hand for short periods for present use, and fre-
quently preserve them when the supply is abundant for use later when
fresh eggs are less plentiful. Eggs for present use, that is, those
stored for a short time only, should be kept where it is cool and mod-
erately dry—in a refrigerator, for instance, a dry cellar or some simi-
lar place. Since they will absorb odors they should be kept away
from strong-smelling substances. With such precautions eggs fresh
at the start will keep in good condition for use in cookery, as most
housekeepers know, for at least two or three weeks. If infertile, they
keep longer and in better condition. When one wishes to keep them
for a still longer period there are methods of preserving them which
can be followed at home with good results.

In general household methods of preserving eggs depend upon the
fact that when the pores of the shell are closed, decay is hindered. The
reason is that this prevents the entrance of molds and bacteria and
hinders the growth of any that may be already present. Among
methods often used with more or less success to stop the pores are

yy BULLETIN 471, U. S. DEPARTMENT OF AGRICULTURE.

burying eggs in oats, bran, or salt; rubbing them with butter; dip-
ping them in melted paraffin; covering them with varnish or shel-
lac; or putting them down in limewater or in a solution of water
glass.

As the result of many trials in farm and other homes, as well as at
the experiment stations, it is generally agreed that putting down eggs
in a solution of water glass or in limewater gives more satisfactory
_results under home conditions than the other methods mentioned.

Water glass is a popular name for both potassium and sodium sili-
cate. The commercial article (often a mixture of the two) is cheaper
and should be used rather than the “chemically pure” water glass
for preserving eggs. It is commonly sold as a siruplike liquid, some-
times as low as 1.75 cents per pound in carboy lots, the retail price
being perhaps 10 cents per pound on an average.

A solution of the desired strength for preserving eggs may be made
by dissolving 1 part of the siruplike water glass in 10 parts by meas-
ure of pure water, preferably water which has been boiled to make
sure that it is free from mold spores, bacteria, etc. A gallon of the
water glass will make solution enough to cover 50 dozen eggs if they
are carefully packed.

The eggs should be as fresh as possible (if infertile, so much the
better), and packed in a crock, keg, or barrel thoroughly washed and
scalded just before its use. Sufficient solution should be poured over
the eggs to cover them well. They should be stored in a cool place,
not only to prevent the growth of any microorganisms which may
have been present before the water glass sealed the pores of the egg-
shells, but also because water glass will occasionally deposit in patches
on the shells if the room is warm.

Many teachers of home economics and housekeepers have asked
whether or not water-glass solution can be used a second time. Occa-
sionally this might answer, but since it is far from certain it is not
desirable nor worth the risk.

The shells of eggs put down in water glass sometimes crack in boil-
ing, but this can be prevented by sticking a pin through the shell into
the air space at the blunt end of the egg before it is boiled.

Limewater, which some consider as satisfactory for preserving
eggs, is shghtly less expensive than water glass. A solution is made
by placing 2 or 3 pounds of unslacked lime in 5 gallons of water
and allowing the mixture to stand until the lime settles and the
liquid is clear. The eggs should be placed in a clean earthenware
jar or other suitable vessel, and covered with the clear limewater.
Sometimes a pound of salt is used with the lime, but many persons
believe that when this is done the eggs have a slight taste of lime.

Eggs preserved in water-glass solution or in limewater answer
admirably most purposes for cookery. Some do not consider them

EGGS AND THEIR VALUE AS FOOD. 93

entirely satisfactory for table purposes, while others do not object
to them. Naturally they are used most acceptably in an omelet
seasoned with onion, tomato, or chopped green pepper, or in some
other form in which seasoning can be used to cover the taste of the
egg: .

Though many housekeepers can depend upon fresh eggs and eggs
stored at home, a larger number must depend upon those which they
purchase, and this almost invariably means a dependence for some
part of the time upon eggs commercially stored.

Commercial preservation of eggs, which is largely preserving by
cold storage, is an industry which has developed very greatly in
recent years. The success of cold storage depends upon the fact that
low temperature is unfavorable to spoiling; that is, to putrefactive
changes, growth of molds, etc., brought about by microorganisms.
The development of methods of artificial refrigeration have made
possible the use of low temperature for this purpose.

In order that advantage may be taken of favorable climatic con-
ditions, eggs are commonly purchased for storage as early in the
year as they are abundant, rather than in the hot months. Since the
infertile eggs keep better than fertile ones, they are given the prefer-
ence for cold storage. It is obvious that the better the egg when it
goes into storage the better its quality when used. Within the usual
limits of storage, perhaps from six to nine months, eggs do not de-
teriorate much, and it is not the case, as many teachers of home
economics and housekeepers believe, that the shorter the time of stor-
age the better the quality. Fuirst-quality storage eggs, on the whole,
compare favorably with any except the better grades of fresh eggs,
and are certainly more desirable than late summer or early autumn
eggs held over by the producer in the hope of securing better prices.
As regards their use in the home, cold-storage eggs of good quality
are very satisfactory for cookery, and, indeed, many persons find
them satisfactory for table use, though those who are very particular
about such matters will no doubt always prefer a new-laid egg.

In considering the whole question the housekeeper and the student
of home problems should realize that the fact that storage tends to
equalize the market and that in many cases one would have difficulty
in procuring eggs at all if one could not depend upon those which
have been stored.

These matters have been considered here from the standpoint of
the home supply and the use of eggs in the home. Those who wish
information regarding the production, marketing, or storage of eggs
should consult the publications of the Animal Husbandry Division,
Bureau of Animal Industry, and of the Bureau of Chemistry.

Whatever her supply, whether fresh eggs, eggs preserved at home,
or cold-storage eggs, the housekeeper who wishes to economize should

24 BULLETIN 471, U. 8S. DEPARTMENT OF AGRICULTURE.

realize that she should use eggs most freely when they are most
abundant and cheapest. When they are high in price she will either
give preference to recipes which call for fewer eggs or she will choose
dishes which do not require eggs, and to keep up the nutritive value of
the diet will depend more upon milk, cheese, meat, and other things
which are similar to eggs in respect to the food materials they
supply.

FROZEN EGGS, DESICCATED EGGS, AND EGG SUBSTITUTES.

Though eggs, like other animal foods, will keep for a long time
when frozen, housekeepers rarely resort to this methed of preserving
them. It sometimes happens, however, that eggs freeze accidentally.
When this is the case they should be thawed slowly (which may be
easily accomplished by putting them into cold water and allowing
them to stand a sufficient time in a cool place) and used at once.

Commercial frozen eggs—that is, eggs broken and frozen in large
containers, with whites and yolks either separate or mixed—are a
common product and have found considerable popularity in bakeries
and restaurants, where eggs are used in quantity. Obviously, the
quality of the product depends upon the grade of the eggs frozen as
well as upon the method of handling.

Preserving foods by drying them is a method which is common
and often very satisfactory. Many housekeepers find it convenient
now and then to dry a few egg whites for use in settling coffee or for
some similar purpose. This can be done by spreading the white in
a thin layer on a platter or other suitable dish and drying it at a
gentle heat in the oven or in the sun.

Several different methods are employed commercially in the prep-
aration of egg powders or desiccated eggs true to name. The whole
egg may be dried, or the white, or the yolk. The process varies
somewhat, the product being sometimes flaky and sometimes a fine,
smooth powder. Im general, 90 per cent of the water originally
present is removed.

As regards composition, desiccated eggs (see table, p. 6) closely
resemble eggs from which the bulk of the water has been removed.
Since fresh eggs contain about 75 per cent of water, it would take
about 4 pounds to make 1 pound of dry egg. In general, desiccated
eggs are readily prepared for use by mixing with a small quantity of
water, and practical tests have shown that they give fairly good
results when used in cookery. It is also possible to use them, thor-
oughly mixed with a small quantity of water, for omelets, etc.
According to observation, desiccated eggs keep well and are whole-
some if well made and handled. Like frozen eggs, they have much
the same food value as fresh eggs. At present they are used chiefly
by bakers, being generally cheaper than fresh eggs, particularly in

—— es ee

———- v- ~

EGGS AND THEIR VALUE AS FOOD. 95

a time of scarcity. They are of interest to the housekeeper as she
may find them at times very convenient or economical—for instance.
for use on a family camping trip.

As previously stated, eggs are used in cookery for their effects upon
consistency and quality of foods as well as for their food value. As
many housekeepers know it is possible, when eggs are lacking, to
use other foods which will give something the same appearance as
eggs; for instance, flour or starch may be used to thicken custards
or gelatin used in making an icing or a pudding. The dish may be
acceptable, but it goes without saying that the food value would not
be the same as if eggs were used.

There are a number of commercial products designed as egg sub-
stitutes, some of which approach eggs in composition much more
nearly than others. Of these products some are fairly well known to
housekeepers, while some are used chiefly in commercial baking and
for similar purposes. The various kinds differ much in composition,
some being much more like eggs in protein content and energy value
than others. In judging such products one should not rely upon
appearance, for yellow color does not necessarily indicate other egg
yolk characteristics. Some of these egg substitutes, at least, are
manufactured from skim milk and are said to contain milk casein
and albumin mixed with a little flour. Such a product is evidently
rich in protein. Other egg substitutes have been devised which con-
sist of mixtures of animal or vegetable fats, albumin, and starch or
flour.

Goods have also been marketed for use as egg substitutes which
contain little or no albumin, but which are apparently made up quite
largely of starch, colored more or less with some yellow substance.
They are commonly advertised for making custards and puddings
similar in appearance to those in which fresh eggs are used. If the
housekeeper wishes to use them she should not overlook the fact that
in the diet they can not replace fresh eggs, since they do not contain
the same kind or quantity of nitrogenous matter or fat. This may be
an important matter, particularly if such an egg substitute is used in
_the diet of invalids or children in the belief that it contains the same
nutrients as eggs.

IMPORTANCE OF EGGS AS FOOD AND THEIR PLACE IN THE DIET.

That eggs are of great importance in the list of foodstuffs is shown
by the last census report, which gives the number produced on farms
in 1909 as 1,457,000,000 dozen, or 16 dozen per capita. Their total
value was estimated at $306,688,960. If the eggs produced elsewhere
than on farms were included this value would be considerably in-
ereased. The value per dozen ranged from 15.9 cents to 27.5 cents,
with 19.3 cents as the average, and was greatest near large cities,

26 BULLETIN 471, U. S. DEPARTMENT OF AGRICULTURE.

in mining districts, and in such sections as Alaska and Hawaii, where
the egg production was very small as compared with the popula-
tion and most of the eggs were shipped from a great distance.

The growing importance of eggs is also shown by the growth of
the industry. The United States formerly imported a large number
of eggs and exported very few. The ratio has changed within recent
years, and now the exports largely exceed the imports as the follow-
ing figures indicate. In 1890 the total number of eggs exported was
381,000 dozen, worth $59,000. In the 12 months ended June, 1915,
is was 20,784,424 dozen, worth $5,003,764. In 1890 this country im-
ported 15,000,000 dozen eggs, which were valued at $2,000,000, and
in 1915 only about 3,046,631 dozen, valued at about $438,760.

Eggs are used in nearly every household almost every day in one
form or another and in varying amounts. From the results of
numerous dietary studies it has appeared that on an average eggs
furnish 3 per cent of the total food, 5.9 per cent of the total protein,
and 4.3 per cent of the total fat used per man per day. For com-
parison it may be noted that cheese furnishes 0.4 per cent of the
total food, 1.6 per cent of the total protein, and 1.6 per cent of the
total fat, while milk and cream together furnish 19.9 per cent of
the total food, 10.5 per cent of the total protein, and 10.7 per cent of
the total fat, in addition to some carbohydrates (which eggs and
cheese do not supply in appreciable quantities), and veal and beef
together were found to furnish 10.3 per cent of the total food, 24.6
per cent of the total protein, and 19.5 per cent of the total fat.

The amount of nutritive material which a given quantity of eggs
will furnish at any stated price per dozen may be readily calculated.
When eggs are 25 cents per dozen, 10 cents expended for them will
furnish 0.60 pound of total food material containing 0.08 pound of
protein and 0.05-pound of fat, the whole having a fuel value of 380
calories. At 35 cents per dozen, 10 cents will procure 0.43 pound of
total food material, containing 0.06 pound of protein and 0.04 pound
of fat, and furnish 275 calories of energy. At 45 cents per dozen,
10 cents’ worth of eggs will furnish 0.33 pound of total food material.
supplying 0.04 pound of protein, 0.03 pound of fat, and 210 calories.
Ten cents expended for beef at 16 cents per pound will furnish 0.63
pound of total food material, containing 0.12 pound of protein and
0.08 pound of fat and supplying 560 calories. Expended for beef
sirloin at 30 cents per pound, 10 cents will furnish 0.33 pound of total
food material, containing 0.05 pound of protein and 0.06 pound of
fat and supplying 345 calories. If wheat bread is purchased at 5
cents per pound, 10 cents will pay for 2 pounds of total food mate-
rial, containing 0.18 pound of protein, 0.03 pound of fat, and 1.06
pounds of carbohydrates, and yielding 2.430 calories.

EGGS AND THEIR VALUE AS FOOD. OE GE

The relative economy of different kinds of food often depends on
more than the amount of nutrients which can be purchased for a
given sum. This is especially true in the case of eggs, which not only
give variety to the diet and furnish an easily digested, nutritious
food, especially suitable for breakfast or other light meal (an im-
portant item for those of sedentary habits), but also are almost indis-
pensable in many kinds of cooking. It should never be forgotten
that when eggs are used in making fancy breads, cakes, desserts, etc.,
they not only improve the appearance, texture, and flavor of the dish,
but also increase its nutritive value.

Many families of moderate means make a practice of buying fresh
meat for but one meal a day—that is, dinner—using for breakfast
either bacon, dried beef, codfish, or left-over meats, etc., and for
lunch or supper bread and butter and the cold meat and other foods
remaining from the other two meals, with perhaps the addition of
cake and fresh or preserved fruit. It is the thrifty housekeeper, who
uses all her material as economically as possible in some such way,
who is likely to fall into the error of excluding eggs at higher prices
almost entirely from her food supply. If her economy were directed
principally to restricting the use of eggs in the making of rich des-
sert dishes, cake, and pastry, one might not only refrain from criti-
cizing, but welcome the circumstances which necessitated the making
of simpler and therefore more wholesome desserts, but usually the
housekeeper economizes on eggs by the more obvious method of omit-
ting to serve them as a meat substitute.

The statement so frequently made by housekeepers that eggs at
a relatively high price are cheaper than meat at a relatively low
price is true in one sense, not, of course, with reference to the total
amount of nutrients obtained for the money expended, but because
a smaller amount of money is needed to furnish the meal. That is
to say, whereas 1.25 pounds of beefsteak, costing 40 cents, at 32
cents per pound, would barely suffice to serve five adults, in many
families five eggs, costing 17 cents, at 40 cents per dozen, would
serve the same number and probably satisfy them equally well. If
the appetites of the family are such as to demand two eggs per per-
son, doubling the cost, they still cost less than the steak at the as-
sumed prices. Many persons eat more than two eggs at a meal, but
the average number served per person, it is believed, does not gen-
erally exceed two in most families, and experience has shown that
very commonly orders in a hotel restaurant are for one egg. Fre-
quently when omelets, soufflés, creamed eggs, and other similar dishes
are served in place of meat or fried, poached, or boiled eggs, less
than one egg per person is used.

98 BULLETIN 471, U. S. DEPARTMENT OF AGRICULTURE.

These statements must not be understood as advocating a free use
of eggs at any price, but merely as pointing out that even at the
higher prices the occasional use of eggs in place of meat need not be
regarded as a luxury. This is illustrated by observations made by
Miss Isabel Bevier and Miss M. E. Sprague’ during a dietary study
of some 115 women, most of them college students. It was found that
the amount of certain foods required for a single meal, when any one
of them was served, was: Beefsteak, 36 pounds; mutton chops, 45
pounds; hamburg steak, 24 pounds; sausage, 30 pounds; bacon, 12
pounds; dried beef, 4 pounds; and eggs, 15 pounds, or 10 dozen.

At the price at which board was furnished, steaks and chops were
too expensive for use as breakfast dishes. At the time the study was
made bacon and dried beef were both considered cheap. Hamburg
steak and sausage were regarded as practicable and were occasionally
used, but eggs at 22 cents per dozen were thought expensive and at 25
cents per dozen so dear that they could not be used. Yet, as the study
showed, at either price the quantity of eggs actually required to
satisfy the members of the club cost less than the amount needed of
any of the foods except bacon and dried beef. Furthermore, it was
easier to utilize boiled eggs not consumed at table than the left-overs
of meat. It appears, therefore, that in this case, as regards both
economy and palatability, the use of eggs as a breakfast dish was
warranted, and the problem discussed is one worth a housekeeper’s
attention.

The eggs, the steaks, and other materials used were not equivalent
in nutritive value, but it must be remembered that other foods were
served with the meat or eggs, and that the total amount of nutrients
consumed at the meal need not have varied greatly from day to day,
although the menu was quite different. Variety from meal to meal
and from day to day is recognized as desirable in the daily diet, and
this is another reason why such uses of eggs are worth considering.

It is generally recognized that eggs require less time and labor for
cooking than most common foods, and for this reason their use as the
hot dish at a meal may often be an economy. There are undoubtedly
cases in which a small saving of gas or other fuel is of importance,
but in many others it is less important than a saving of time or labor.
Without question a reason for the popularity of eggs in most house-
holds is that they may be so easily and quickly prepared for the table
in appetizing ways.

In the case of eggs, like other foods, the income and the need for
economy must determine how far and in what ways they are to be
used when they are high in price. Judged by their composition and
digestibility, eggs are worthy of the high opinion in which they are

1U. S. Dept. Agr., Office Expt. Stas. Bul. 91 (1900), and unpublished data furnished by
Miss Sprague.

— = - w

EGGS AND THEIR VALUE AS FOOD. 29

usually held. Furthermore, they are generally relished. Although
the physiological reasons were perhaps difficult to find, it was long
ago conceded that the attractiveness and palatability of any food
must not be forgotten in considering its true nutritive value. Refine-
ment in matters of diet should keep pace with growth in general cul-
ture, and foods which please the esthetic sense as well as satisfy
hunger are certainly to be preferred to those which serve the latter
purpose only, if they can be obtained with the income at one’s com-
mand.

PUBLICATIONS BY THE U. S. DEPARTMENT OF AGRICULTURE OF
INTEREST IN CONNECTION WITH THIS BULEETIN.

Yearbook 1910, The effect of the present method of handling eggs on the indus-
try and the product.

Yearbook 1912, How the produce dealer may improve the quality of poultry and
eggs,

Yearbook 1914, Egg and poultry demonstration-car work in reducing our $50,-
000,000 waste in eggs.

Farmers’ Bul. 142, Principles of nutrition and nutritive value of food.

Farmers’ Bul. 445, Marketing eggs through the creamery.

Farmers’ Bul. 594, Shipping eggs by parcel post.

Farmers’ Bul. 656, The community egg circle.

Department Bul. 51, A bacteriological and chemical study of commercial eggs
in the producing districts of the Central West. ’

Department Bul. 224, A study of the preparation of frozen and dried eggs in the
producing section.

Bur. Anim. Indus. Circ. 140, The egg trade of the United States.

Bur. Anim. Indus. Bul. 141, The improvement of the farm egg.

Bur. Anim. Indus. Bul. 160, The care of the farm eggs.

Bur. Chem. Cire. 64, Studies of poultry from the farm to the consumer.

Bur. Chem. Cire. 83, Deterioration of egzs as shown by changes in the moisture
content.

Bur. Chem. Cire. 98, Practical suggestions for the preparation of frozen and dried
eggs.

Bur. Chem. Cire. 104, A study of the enzyms of the egg of the common fowl.

Bur. Chem. Bul. 115, A preliminary study of the effects of cold storage on eggs,
quail, and chickens,

Bur. Chem. Bul. 158, A bacteriological study of shell, frozen, and desiccated eggs.

Bur. Statis. Bul. 938, Cold-storage business features.

Bur. Statis. Bul. 101, Cold storage and prices.

30

WASHINGTON : GOVERNMENT PRINTING OFFICE : 1916

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